Study On Treatment Of Oil Recovery Sewage By DC Electrocoagulation Method

Recently, due to the changing from primary oil recovery, that is mechanical recovery using reservoir energy, to secondary oil recovery, that is water flooding, the study on oil recovery sewage treatment technology, which is simple, effective, cheap and environment-friendly, is necessary. Electrocoagulation is a good choice because the process was found to be highly operable and effective, with the characteristics of compact, facilitated operation and higher efficiency against hydraulic loading shock. It conquers the limitation of conventional three sections process which chemical adding a lot. As a result, oil recovery sewage which is has been treated will not destroy the ecology environment underground. At the same time, there is not additional burden in the subsequent processes while it is recovered at the next period. A serious of study on operating condition and energy consumption is carried out and to establish the foundation for application and popularization of the technology. This paper made studies mainly on the following four aspects.First of all, different electrode materials and operational conditions were examined. Laboratory test showed that iron electrode was preferred to aluminium's. As to the connection method of electrodes, single-polar connection is better than the other ways of electrodes connection.Then, the effects on the removal rate of physicochemical index and energy consumption affected by some influential factors had been investigated thoroughly. Laboratory test showed that after treatment the wastewater will completely come up to the standard of refilling water for oilfields. This means that the EC presents a feasible alternative in dealing with oil field sewage; pH value should be controlled about 7, which can make high removal efficiency about turbidity and oil; the current density should be controlled about 4A/dm2 and the electrode distance changed between 10～20mm.What's more, we use the EC to remove bacteria in oil recovery sewage which contained the most harmful kinds of bacteria (SRB, IB, TGB), and to study the mechanism of removal bacteria as well as sterilization.The results indicated that it has a good effect on all of the three. And it also confirmed, under electrical field, that is, physical effect and coagulation, it could kill the bacteria directly, however, the sterilization rate was relatively low, which cannot meet the standard of refilling water for oilfields. With the extension of the static duration, the sterilization rate increased greatly. In the effluent water, TGB reaches≤103/ml,IB is almost 0 in the most cases, SRB comes up to the standard as well.Finally, a series of experiments were designed to study the electrochemical behavior of sacrificial anode and load characteristics of oil recovery sewage by EC with DC power supply. Due to the highly mineralized water, the polarization curves of two kinds of electrodes show that active dissolution, almost has no passivation. Moreover, the open circuit potential both moved toward the negative direction in that water sample. Cyclic voltammetry indicate that both electrodes have a direct electrochemical oxidation of pollutants in oil recovery sewage. Meanwhile, according to the theory, linear and non-linear regression models of oil recovery sewage purified by EC with DC power supply are established.